--- title: What are the Most Common Authentication Vulnerabilities? description: An overview of the most common authentication vulnerabilities in software applications, covering both broken authentication issues (flawed logic, weak recovery... canonical: https://daily.dev/posts/what-are-the-most-common-authentication-vulnerabilities--su9ypsn5b twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: What are the Most Common Authentication Vulnerabilities? | daily.dev og:description: An overview of the most common authentication vulnerabilities in software applications, covering both broken authentication issues (flawed logic, weak recovery... og:url: https://daily.dev/posts/what-are-the-most-common-authentication-vulnerabilities--su9ypsn5b og:image: https://api.daily.dev/og/posts/Su9ypsN5b.png og:image:alt: What are the Most Common Authentication Vulnerabilities? og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # What are the Most Common Authentication Vulnerabilities? **[Teleport](https://daily.dev/sources/teleport)** · 6 min read · 0 upvotes · 0 comments ## Summary An overview of the most common authentication vulnerabilities in software applications, covering both broken authentication issues (flawed logic, weak recovery processes, vulnerable dependencies, insecure session handling, missing rate limiters, and flawed 2FA implementations) and password-related issues (insecure hash functions like MD5, poor password policy enforcement). It cites real-world examples such as Google account recovery hijacking, WordPress plugin authentication bypass, PayPal and Box 2FA bypasses, and explains common attack vectors like phishing, brute-force, dictionary/rainbow table attacks, and SQL injection. Closes with a pitch for Teleport's certificate-based passwordless authentication. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### Why is SMS-based two-factor authentication considered insecure? SMS and phone-based verification for two-factor authentication are considered insecure because the delivery channel itself can be intercepted or hijacked, undermining the extra security layer 2FA is meant to provide. This is a known weakness distinct from implementation bugs, since even a correctly coded SMS 2FA flow inherits the risks of the SMS channel. _Teams weighing 2FA methods can track evolving authentication security guidance on daily.dev._ ### How was PayPal's two-factor authentication bypassed by security researchers? Duo Labs researchers bypassed PayPal's two-factor authentication by exploiting insecure enforcement of 2FA in PayPal's REST API when users authenticated via OAuth, allowing the second factor check to be skipped entirely. This is an example of a broken authentication flaw rather than a weakness in the 2FA algorithm itself. _Developers hardening OAuth and 2FA flows can follow real-world bypass writeups like this on daily.dev._ ### What made Box's two-factor authentication vulnerable to bypass? Box's two-factor authentication could be disabled without requiring any authentication, meaning an attacker could turn off a victim's 2FA and then log in with just the password. Varonis researchers uncovered this flaw, illustrating how a missing authentication check on a sensitive account setting can nullify an otherwise sound 2FA system. _Engineers auditing account-security settings can find similar vulnerability breakdowns on daily.dev._ ## Similar posts on daily.dev - [The 5 Most Common API Vulnerabilities in 2026](https://daily.dev/posts/the-5-most-common-api-vulnerabilities-in-2026-w5nu178fs) · Nordic APIs · 0 upvotes · 0 comments - [Cryptographic Failures in Authentication and Session Management](https://daily.dev/posts/cryptographic-failures-in-authentication-and-session-management-vqte7bxll) · Security Boulevard · 0 upvotes · 0 comments - [API Attack Awareness: When Authentication Fails — Exposing APIs to Risk](https://daily.dev/posts/api-attack-awareness-when-authentication-fails-exposing-apis-to-risk-4idckpdli) · Security Boulevard · 0 upvotes · 0 comments --- Tags: [#authentication](https://daily.dev/tags/authentication), [#sql](https://daily.dev/tags/sql), [#appsec](https://daily.dev/tags/appsec) [View this post on daily.dev](https://daily.dev/posts/what-are-the-most-common-authentication-vulnerabilities--su9ypsn5b) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"What are the Most Common Authentication Vulnerabilities?","url":"https://daily.dev/posts/what-are-the-most-common-authentication-vulnerabilities--su9ypsn5b","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/what-are-the-most-common-authentication-vulnerabilities--su9ypsn5b"},"datePublished":"2026-08-23T12:22:56.836Z","dateModified":"2026-08-23T12:52:37.424Z","description":"An overview of the most common authentication vulnerabilities in software applications, covering both broken authentication issues (flawed logic, weak recovery...","image":"https://media.daily.dev/image/upload/s--qPvKM23u--/f_auto/v1722860399/public/Placeholder%2009","thumbnailUrl":"https://media.daily.dev/image/upload/s--qPvKM23u--/f_auto/v1722860399/public/Placeholder%2009","isAccessibleForFree":true,"articleSection":"Teleport","inLanguage":"en","publisher":{"@type":"Organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180}},"author":{"@type":"Organization","name":"Teleport","logo":"https://media.daily.dev/image/upload/s--Dw-Bbw6O--/c_limit,w_256/f_auto,q_auto/v1787487494/logos/teleport?_a=BAMAMicg0","url":"https://daily.dev/sources/teleport"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/what-are-the-most-common-authentication-vulnerabilities--su9ypsn5b","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"authentication,sql,appsec","timeRequired":"PT6M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"Teleport","item":"https://daily.dev/sources/teleport"},{"@type":"ListItem","position":3,"name":"What are the Most Common Authentication Vulnerabilities?"}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/what-are-the-most-common-authentication-vulnerabilities--su9ypsn5b#faq","mainEntity":[{"@type":"Question","name":"Why is SMS-based two-factor authentication considered insecure?","acceptedAnswer":{"@type":"Answer","text":"SMS and phone-based verification for two-factor authentication are considered insecure because the delivery channel itself can be intercepted or hijacked, undermining the extra security layer 2FA is meant to provide. 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